The window size is defined as the area of the glass. This area is calculated from the rectangular dimensions of the glass plate as determined through direct measurement using a standard tape measure of appropriate length. Once the dimensions of the window have been determined the area of the window is calculated by multiplying the glass length by the glass width.

As a general rule:

The use of solar control film is not recommended for monolithic annealed glass with areas in excess of 100 sq ft.

The use of solar control film is not recommended for annealed insulating glass units in excess of 40 sq ft.

The use of solar control film is not recommended for annealed laminated glass of any thickness.

*Check your film manufacturer's guidelines for specific recommendations regarding these special conditions.